Minnesota Vikings running back Adrian Peterson takes the field against the Chicago Bears at Mall of America Field at the Hubert Humphrey Metrodome. (Dec. 1, 2013) Photo Credit: Getty

ACL injuries are down, the NFL has told its Health and Safety Advisory Committee.

In a memo to the committee sent earlier this week and obtained by The Associated Press, the league said research showed there were 30 ACL injuries in games through the preseason and first 13 weeks of the schedule. There were 39 such injuries in 2012, 35 in 2011, 37 in 2010, and 31 in 2009.

Anterior cruciate ligament problems are the most severe knee injuries.

There was an increase in medial collateral ligament injuries (MCL), from 74 in 2012 to 89 in games this season through 13 weeks. But there were 106 MCL injuries in 2011, 89 in 2010 and 103 in 2009.

The injury reporting service Quintiles/Outcome provided the numbers to the league, which then sent them to the committee chaired by 49ers owner John York. The committee also includes Giants owner John Mara, Cowboys owner Jerry Jones, Packers President Mark Murphy and Falcons President Rich McKay. The data are for all types of ACL and MCL injuries, including tears and sprains.

There have been suggestions that knee injuries have gone up since the NFL cracked down heavily on hits to the head and neck area. While there have been several high-profile hits to the knee that sidelined players — New England tight end Rob Gronkowski, for example — the league-requested survey of this year's injuries does not indicate a trend toward increased major knee problems through 13 weeks.

Earlier this week, Patriots coach Bill Belichick claimed injuries were up. He didn't cite specific numbers, but said it was "a matter of record not opinion" that injuries league-wide have been on the rise over the past three years.

Belichick blamed a decrease in the number of offseason, preseason and in-season practice sessions and workouts allowed as a main contributor to higher injury totals.

League spokesman Michael Signora disputed Belichick's assertions.

"We carefully monitor player injuries," Signora said. "There is no evidence that the new work rules have had an adverse effect on the injury rate or that injuries have in fact increased."

And with the ACL injuries, the research by Quintiles/Outcome shows the opposite.

This season through 13 weeks, about 68 percent of ACL injuries involved contact with another player. The percentage in the four previous seasons ranged from 67 percent in 2009 to 55 percent in 2012.

A breakdown by positions showed one tight end, one wide receiver and one quarterback had contact-related ACL injuries through 13 weeks this season. That compares to five such injuries combined at those positions in 2012 and four in 2011.

For offensive players in general, there have been six such injuries in 2013 through 13 weeks, compared to 10 in 2012, eight in 2011, nine in 2010 and six in 2009.

On defense, there were six ACL injuries involving contact with another player. This compares to nine such injuries in 2012, 10 in 2011, nine in 2010, and seven in 2009.